Both glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are peptides called incretin. GLP-1 and GIP are secreted from small intestinal L cells and K cells, respectively.
GLP-1 acts via GLP-1 receptors and is known to have a glucose-dependent insulinotropic action and a feeding suppressive action. On the other hand, GIP is known to have a glucose-dependent insulinotropic action via GIP receptors, though its influence on feeding is not clear.
The co-administration of a GLP-1 receptor agonist liraglutide and a GIP receptor agonist N-Ac-GIP has been reported to more promote a glucose tolerance-improving action and a body weight-lowering action than the administration of liraglutide alone (Non Patent Literature 1). Also, a GLP-1 receptor/GIP receptor coagonist peptide has been reported to show a stronger hypoglycemic action and body weight-lowering action than those of a GLP-1 receptor agonist alone (Patent Literature 1).
Attempts have also been made to search for peptides having GLP-1 receptor/GIP receptor coagonist or glucagon/GLP-1 receptor/GIP receptor triagonist activity and develop these peptides as anti-obesity drugs or therapeutic drugs for diabetes, on the basis of the structure of natural glucagon, GIP, or GLP-1 (Patent Literatures 1 to 8). None of the literatures, however, disclose the peptide compound of the present invention.